Document Sample

                             EVS By—Kaxil Naik


1.   Introduction to Environment, Ecology and Ecosystem.
2.   Ecology and Ecosystem.
3.   Population and natural resources.
4.   Environmental Pollution.

     Reference Books:

1.   Basics of Environmental Studies by N.S. Varandai.
2.   Introduction to Environmental Engineering and Science by Master Gilbert.
3.   Environmental Engineering and management by Suresh K. Dahnja.
4.   Perspective in Environmental Studies by Kaushik and Kaushik.
5.   Environmental Studies by R. Rajagopalachari.

                 AND ECOSYSTEM

Living means biotic Non-living means Abiotic

Man cannot survive alone or aloof. He needs the help of the organisms and the
immediate surrounding for his survival. The surrounding of any living organism
with which it interacts and exchange matter and energy is known as its
environment. It is defined from French word “Environ” meaning “Encircle”.

Environment has 2 parts: -
   (1) Biotic Component                     (2) Abiotic Component

(1) Biotic Component: It includes all the living entities e.g. Man, Animal, Bird etc…
(2) Abiotic Component: It includes soil, air, water, light etc…

Various life supporting systems e.g. oceans, mountains, desert etc. have different
structure and function.
All the system definitely has the living entities which invariably exchange matter
and energy i.e. interact with the other living organisms and non-living environment.
The study of this relation is known as ECOLOGY.

ECOLOGY is defined from two Greek words “ockus” [house/habitat] +
“logus” [study].

ECOLOGY is also defined as study of various ecosystems.

ECOSYSTEM is defined as self-regulating group of biotic community i.e. living
organisms with abiotic community i.e. non-living part forming a self-supporting
system. Various ecosystems exist like pond, lake, mountain, desert, grassland,
forest etc.


             WATER                    LIVING                 SOIL

                                   MATERIAL IN


 The global environment is divided into 4 parts:

       (1) Atmosphere
       (2) Hydrosphere
       (3) Lithosphere
       (4) Biosphere


        It is a complex mixture of gases, dust particles and water-vapours. About
 15.5 x 1015 metric ton of the gases surround our planet. Atmosphere is further
 divided into different layers depending on the change in the slope of the graph with

 i.    Troposphere: It is the lowermost layer of atmosphere which is in direct
       contact with the earth’s surface. The concentration of dust particles varies
       drastically. It is the region of air movements and the cloud formation. The
       temperature goes up to -80C. The height of troposphere is 20 km above
       equator and 9 km above the poles. The composition of air in troposphere is as
       follows: N2=78%, O2=21%, Ar=0.94% and CO2=0.03% approx.

ii.    Stratosphere: This layer extends up to 50 km from the earth’s crust. In this
       region due to presence of ultraviolet light, the photochemical reaction between
       O2 molecules occur to produce ozone. It is a continuous process and is
       exothermic. Due to this heat the temperature of this region rises up to 0C.
       0C is at Stratopause.

                                  O2 + hv  2 O + 
                                  O2 + O     O3 + 
       This layer is also named as ozonosphere and serves as a protective shield for
       the mankind.

iii.   Mesosphere: It extends up to 80-90 km above earth’s surface. The
       temperature declines up to -95C in this region.

iv.    Thermosphere: It is also known as Ionosphere. In this layer continuous
       dissociation of O2 molecules occur and temperature increases continuously.
       This layer extends up to 500 km above earth’s surface.

v.     Exosphere: It extends up to 31,290 km. Temperature continuously increases
       and contains gases like H2 and He.


      We know that 4/5th part of earth’s surface is covered with water.
      97% of it is locked in oceans and seas because it is highly salty.
      Roughly 2% exist in polar ice-caps and glaciers.

      About remaining 1% is available in form of various water-bodies like rivers,
       ponds, lakes etc for use of mankind.

 Water is mainly used by man for the following purposes: -

 (1)   In irrigation: 30% of water is used.
 (2)   In Thermal Power Plants: 50% of water is used.
 (3)   Domestic Used: 7%.
 (4)   Industrial Use: 30%.
 (5)   Evaporation: 10%.

 Water has certain unique properties due to which it is used abundantly.

 [1] It has very high surface tension. This property makes it possible to be
     retained in the soil by the capillary action.
 [2] Its density is maximum at 4C which allows its solid form i.e. ice to float on the
     surface. During extreme winter when the temperature decrease the water in
     the water bodies freezes to ice, but it happens only on the surface that allows
     aquatic life to survive.
 [3] The water molecules are bonded strongly by hydrogen bonds. Thus it
     requires very high temperature to evaporation. This makes water stable at a
     wide range of temperature. The liquid form serves as a very good medium to
     carry nutrients.
 [4] It has high heat capacity due to which it is used as a coolant and for
     generation of steam.

   The solid part of the earth is known as lithosphere.
   It is made up of rocks and a loose material made out of it (rock) known as soil.
   Large amount of elements are known to exist which combine in various
    proportions to form minerals. These minerals constitute the rocks.
  Lithosphere is divided into 4 layers moving downwards.
 i. First layer is known as EARTH’S CRUST.
  It extends up to 17 km downwards.
  It is solid part which is made up of various minerals.
  The Biosphere exists in this region.

ii. Second layer is known as MANTLE.
  It extends up to 2883 km.
  It is solid in nature and it contains silicates.

iii.   Third layer is known as OUTER CORE.
      It extends up to 3471 km.
      It is liquid in nature and it contains mainly Iron and Nickel alloys.
iv.    Fourth layer is known as INNER CORE.
      It extends up to 6371 km.
      It is solid in nature and it contains pure in iron.


The parent rocks which exist on the surface are made up of minerals. Almost 2000
minerals are known to exist. Among them only 10 to 12 minerals form the rocks.
From them main minerals are (i) Feldspar (ii) Pyroxenes (iii) Quartz (iv) Mica.

Rocks which exist on earth’s surfaces are mainly of 3 types: -

(1) Igneous Rocks: These are formed by the cooling and solidification of molten
    metals known as magma. E.g. are Diorite and Basalt etc.
(2) Sedimentary Rocks: These are characterized by the presence of distinct
    sedimentary (deposition of one layer on another) layers. E.g. Sand stone, lime
    stone, slate etc.
(3) Metamorphic Rocks: These are formed by metamorphosis of igneous and
    sedimentary rocks under high temperature and presence. E.g. Quartzite,
    Marble etc.

The formation of rocks and conversion into soil is a cyclic process and happens
due to weathering. The soil formation is known as pedogeneses.

Disintegration of rocks:
 The Disintegration products of the rocks which are sand, silt, gravel and clay
  undergo burial, compaction and hardening to produce sedimentary rocks.
  These rocks under high temperature and pressure transforms into metamorphic
  rocks. The melting, upward movement and re-solidification of the metamorphic
  rocks again generate igneous rocks. The disintegration and formation is a cyclic
  process on a geo-logical time scale. The sand, silt, gravel and clay are the
  intermediates in the cycle.

             S   d s lt g   l   d cl y

                                    (Rock Cycle)


      The earth’s crust is subjected continuously to battering of rain, wind and
changes in temperature. This physical condition causes the disintegration of the
rocks. The modification of the earth’s crust due to battering is known as
weathering, which results into the formation of land having productive soil.
Depending upon the type of agencies, weathering is of 3 types:

1. Physical weathering: It occurs due to mechanical process. The wind
   movements, flowing water causes the rocks to abrade (mean. to rub
   something so hard that the surface becomes damaged). The differential
   thermal expansion and contraction due to the changes in temperature causes
   tensile stress to develop within the rocks, which develops crack. These fine
   cracks gradually convert to gaps and fissures (mean. separation), the
   pressure exerted exceeds the strength of the rock and the rocks break into
   pieces. Simultaneously, the roots of the plants growing on and within the rocks
   cause the fragment of the rock to tear apart.
2. Chemical weathering: It is a slow process and it includes the reactions like
   dissolution, hydration, hydrolysis, carbonation, oxidation and reduction. This
   chemical reaction occurs due to the air which contains moisture, oxygen and
   carbon dioxide.
3. Biological weathering: The plants like mosses, lichens, fungi and algae grow
   inside the rocks due to sufficient amount of moisture and nutrients. They
   metabolize and after death and decay, the microbial action begins. This
   process adds to the organic content of the rocks and the fragment.

    Due to continuous weathering and microbial action, the dead organic matter
    decays, producing simpler compounds like carbohydrates, proteins, fats,
    lignin, resins and waxes. This adds to the nutrient of the weathered rocks
    (soil). The increase in the organic content along with the network of the roots
    of the dead plant increases the porosity and the imbibing (mean. absorption)
    capacity of moisture and nutrients. The residual in completely decomposed
    organic matter along with the microbes is known as humus. The increase in
    the organic compound along with the moisture is known as humification. The
    conversion of organic compound into the elemental nutrients is known as

       All the three processes i.e. weathering, humification and mineralization are
    collectively called pedogeneses of soil formation.

       Besides these, the bacteria converts atmospheric nitrogen and
    phosphorous into useful compounds. The process is called fixation. Certain
    worms increase the porosity of the soil. This kind of good quality soil is used
    by the man in agriculture.

To study them they have divided into smaller units known as ecosystem. Entire
ecosystem can be broadly divided into 2 parts: (1) Abiotic (2) Biotic.
The abiotic components are mainly N2 and P4.
The biotic community which forms biosphere is classified into 3 categories:


 i. Producers: These are the autotrophes i.e. the green plants which are
    manufacturers of food.
ii. Consumers: Consumers are those living beings which depend on other living
    beings for food.

 Consumers are classified in to the following:

  a) Primary Consumers: They are herbivores animals.
  b) Secondary Consumers: They are carnivores or omnivores animals.
  c) Tertiary Consumers: They are those which depend purely on other animals.
  d) Quaternary Consumers: These are the top consumers which are not eaten
     by any other animals. E.g. lion, tiger, leopard, eagle etc.

iii. Decomposers: After the death and decay of all living beings the bacteria and
     fungi decompose them. They are known as environment cleaners. They
     convert the complex organic matter.

       Ever since man has appeared on earth, he began to exploit and modified
 the environment according to his needs for his advantage.


        The typical structure and composition of atmosphere makes it possible to
 create conditions which are suitable for the existence of living beings.
        Almost 20 times greater volume of air is taken inside the body by man when
 compared to the amount of food we eat and water we drink. The air [O 2] which is
 taken inside the body combines in the lungs with the blood forming oxy-
 haemoglobin [O2 + Hb].

                              O2 + Hb  oxy-haemoglobin

        This oxy-haemoglobin travels through various organs of the body through
 the heart. In the organ it breaks back into oxygen and haemoglobin. So the air
 which we breathe should be as clean as possible.
        The air forms a blanket around the globe which regulates the temperature.
 If we compare with atmosphere of moon – where there is no air, temperature
 changes from -180C to 101C, hence there is no life on moon.
        The air current in the atmosphere take place due to the vertical temperature
 gradient. Due to the sun-light, the lowermost layer of atmosphere is heated up,
 becomes light in weight, it rises up and gets replaced by cooler air. The ozone
 layer serves as a preventive shield by absorbing UV-B and UV-C radiation.

        There is availability of water, besides the existence and abundance of
 terrestrial life. The unique feature of water makes the plant and vegetation to
 appear on the earth’s surface. Large amount of water sustains in the soil by
 capillary action due to the surface tension. For e.g. in desert flora (plants) are

     xerophytes and fauna (animals) has modified structure such that it uses less water
     or stores it.


            The life of living beings depends largely on the animals and plants which
     exist on the land. This solid part of the environment provide: (a) Mechanical
     strength: It provides mechanical ground for man and animal to move. (b) It
     provides support to plant such that roots grow inside the soil which anchors the
     shoot. All water-bodies are found on surface of land.

     The systematic exploitation, modification and destruction of environment began
     when man learned to use fibre, domesticate animals and grow plants for its food.
     This relation can be divided into 3 phases:

     1) The phase of hunting and food gathering:
        The primitive man when originated, he lived in caves and on trees; he ate raw
        flesh and any plant product. Slowly with his experience, for his safety, the man
        used stone as his weapon. He started making tools with the stone. During this
        process he discovered spark which caught fire in dry leaves. He used this fire
        initially for protecting himself from wild animals. He roasted flesh and kept
        himself warm.

     2) The phase of domestication of animals and agriculture settlement:
        With the knowledge of fire and discovery of iron, he learnt the use of animals.
        He collected and kept the useful animals at one place, looked after its well-
        being, thus domesticated it.
        At the same time he selected crops and plants which were useful for him,
        cleared the land and planted those useful plants or trees. In this way he began
        the agriculture. For all this purposes he modified land and used water
        extensively from various sources.

     3) The phase of science, technology and industrialization:
        With the advancement of science and technology, the life of man improved
        manifolds with the misuse of environment.

I.     The extraction of metal and its use: It was the first mile-stone in the growth
       and development of mankind around 4000 B.C. The first metal copper was
       extracted and it was to make tools and pans. Although iron was found in
       abundance but still that was not the first metal to be extracted due to following
       Copper was easy to be extracted and it could be purified easily at lower
       temperature whereas it took long period of time to develop the technique to
       extract iron since its purification required very high temperature and specially
       made furnaces. Iron was extracted around 1000 B.C. This was the turning point
       in development of science and technology to its speed.


II.    Expansion of agriculture and animal husbandry: With the growth of
       techniques, the increasing human population require large amount of food. For
       this purpose agriculture was expanded i.e. large areas of land were used to
       grow crops and at the same time large number of animals were utilized for his
       meal. After 1800 A.D. the population was found to be 1 million.
             The high mortality rates due to epidemics, natural disasters like flood,
       earthquake were reduced and it was found that within a very less span of time
       (about 45-50 years), the population doubled. The increasing population had an
       adverse effect on the environment. Many new attributes were added to the
       society due to the technological development.
             (1) Increased medical facility.
             (2) Growth in communication and transportation enabled man to fight
       against natural disaster.
             (3) Development in agricultural techniques gave sufficient and good quality
       food for man.

I.     Impact of mining and extraction:
        a. Defacing and degeneration of the land: The physical presence of
           landscape change. All the plants and trees of the particular area are cleared
           of and the physical appearance of the land along with the composition of
           soil is changed when mining is done.
        b. Subsidence of land: After the mining a gap is created under the ground
           due to which tilting of the building, bending of the roads and the railway
           track take place. This is known as subsidence of land.
        c. Ground water contamination: During the extraction of the minerals
           sulphur in the core converts into H2SO4 by the microbial activity and it adds
           to the water bodies.
        d. Surface water pollution and contamination: The drainage of the mine
           which adds many poisonous elements into water.
        e. Air Pollution: During smelting when the pure minerals are separated, large
           amount of air pollution spreads soot, CO2, metallic particles, lead, cadmium,
           arsenic in air.
        f. Occupational health hazards: The people working in mines suffer from
           various diseases like asthma, skin cancer and various lung diseases.

            Due to overuse of the green grasslands, the environment is affected badly.

II.    Overgrazing:
       a) Soil erosion: The roots of grass and plants bind the soil particles but due to
          overgrazing, the soil is loosened which causes removal of the soil.
       b) Deforestation: Removal of trees and plants from the forest cause
       c) Loss of certain species of plants: Some valuable plants are also eaten by
          animals. It is a major problem.
       d) Due to agricultural techniques:
          (i) Traditional Agricultural Techniques:
           Deforestation: To create more land, the existing trees and plants are to
              be cut, causing deforestation.


             Soil erosion: The large and repeated use of soil causes the decrease in
              the nutrients because the cycling and regeneration of the nutrients is
            (ii) Modern Day Techniques:
                  [1] For the growth of high yield, varieties of chemical fertilizers are
                  [2] The natural pollution occurs. Mithhaemoglobinamea which can cause
                      death to infants.
                  [3] Bio-magnification.
                  [4] Water Pollution.
                  [5] Solid waste disposal.

     The degradation is defined as the destruction or deterioration of the
     environment due to overuse, misuse and addition of unwanted discharges in
     any of the components of environment.
     Due to the anthropogenic activities [activities done by man for his living], the
     environmental degradation occurs.
     During the early development the reasons of environmental degradation were of
     traditional type:
I.     Traditional:
         Poverty and insufficient development.
         Some of them are as follows:
        1. Lack of access [approach] to drinking water.
        2. Insufficient and inadequate sanitation habits in household and communities.
        3. Natural disaster like flood, famine, drought.
        4. Contamination of food.
        5. Attack of pathogens.
        6. Occupational health hazards even in agriculture.

II.    Modern day hazards:
       1. Water pollution
       2. Urban air pollution.
       3. Solid waste disposal.
       4. Chemical and radiation hazards.
       5. Ozone depletion.
       6. Regional degradation.
       7. Temporal changes –GLOBAL WARMING.


      The environmental degradation can be summarized into few following points:
 1.   Pollution.
 2.   Population explosion.
 3.   Exploitation of natural resources.
 4.   Disturbances in ecosystems.
 5.   Accumulation of waste.

      This topic can be asked as 7 marks question. Write above 5 points, then write about
         TRADITIONAL and MODERN DAY HAZARDS and expand it in your own words.


                Ch: 2 ECOLOGY AND ECOSYSTEM

       ECOLOGY IS DERIVED FROM 2 Greek words ‘oikos’=house and ‘logus’=study.

        Basically it is the study of interactions of species of organisms living in
population and communities. They interact within themselves and with the non-
living environment.
        Every living organism or entity is made up of cells. E.g. bacteria, insects,
birds, reptiles, animals, man etc.
        A group of living organisms which are similar in behavior and general
appearance is known as species. Number of species living together in a given
region is known as population.
        Large number of different population living together with mutual interaction
with the energy flow is known as a community. Within a community the
organisms of population interact with each other, derive energy and attain
equilibrium. Such equilibrated community having interaction is known as

1) The inter-relationship between the living and non-living organisms.
2) The independence of all the units present in the eco-system.
3) Study of flow of energy.
4) Study of the reproduction which maintains the balance of ecosystem.
5) The harvesting and management of natural resources which help the
   component of ecosystem.
6) Structural adaptation by the organisms.
7) Evolutionary changes within a community.

       In a nutshell, the objective of study of ecology can be described as the
means to study various adaptations and features of the community of organisms
relating with environment such that man can control the effect of natural disaster.

    The ecologists have classified ecology in various bases:
[1] Basis of dependence:
    (a) Autecology - [study of individual species].
    (b) Synecology - (i) Population, (ii) Community and (iii) Ecosystem.

[2]    Basis of habitat:
      a) Aquatic: (1) Fresh water (2) Marine ecology and (3) Stream water.
      b) Terrestrial: (1) Grassland (2) Forest and (3) Desert.
The latest classification of ecology by ecologists has been done into following
   (1) Pollution ecology.
   (2) Productive ecology.
   (3) Population ecology.

   (4) Community ecology.
   (5) Ecosystem ecology.
   (6) Microbial ecology.
   (7) Radiation ecology.
   (8) Space ecology.

(1) The structural and functional units of the ecosystem are Abiotic and biotic
    components respectively.
(2) Interaction among the organisms within themselves and the environment take
(3) The flow of energy in an ecosystem is unidirectional.
(4) The nutrients involved in an ecosystem flow within in a cyclic manner. They
    are regenerated and recycled.
(5) Depending upon the availability of energy the organisms grow.
(6) Its dispersion and distribution forms the climax of the ecosystem.

Bio-geochemical cycle: The flow of the energy takes place within the organism
from one trophic level to the other with considerable amount of loses. Unlike this
the nutrients flow in a cycle, almost 40 chemical elements are essential for the
growth of an organism. Some of them are known as macro-nutrients for e.g. C, N,
O, P, S etc. They are exchanged with the atmosphere. Some of them are known
as micro-nutrients like Fe, Cu etc. They are used up by the organisms from the
soil. So they are known as EDAPHIC FACTOR (SOIL FACTOR).
       All the nutrients essential for the growth are used by the organism through
the autotrophic plants i.e. producers. They are converted to the required organic
compounds useful for them, used and after their death and decay, are given back
to the various abiotic components of the atmosphere. This flow of nutrients from
inorganic component to living organisms and back to environment with the
intermediate formation of organic compounds is known as Bio-geochemical

(1) HYDROLOGICAL CYCLE: This cycle represents the flow of water from the
environment to the organisms. The water present in the water-bodies and moisture
in the soil gets evaporated when the temperature rises. They are converted into
clouds in the uppermost region of troposphere. This clouds under-pressure gets
precipitated in the form of rain or snow. This water joins back the water-bodies
present on the earth. Simultaneously the natural water is also consumed by plants
and animals. These through their biological process of transpiration and excretion
liberate to the atmosphere which again evaporates and join to form clouds.

                              (Hydrological cycle)


(2) CARBON CYCLE: Carbon is one of the most essential elements. The first
compound of carbon formed by plants through photosynthesis is GLUCOSE
(C6H12O6). It is a 6 carbon compound and has almost 686,000 calories of energy.
This glucose by the plants is then converted to the other useful organic compound
like proteins, enzymes, nucleic acid, etc i.e. the solar radiation are trapped by the
plants, convert heat of the sun to glucose, and this is then converted to organic
compound. The entire organic compound so formed is consumed by the
successive consumer. It provides energy to living beings and help organisms to
grow by the change from one form to the other.
    The first element carbon present in atmosphere is CO2. It is produced and
accumulated. The locations of production of CO2 are:
    (1) Volcanoes and forest fire.
    (2) Weathering of rocks.
    (3) Aerobic and anaerobic respiration by animals.
    (4) Combustion of fuel.
    (5) Formation of new rocks.

   At the same time, CO2 is accumulated in the atmosphere. This CO2 is then
used in the various natural processes. The CO2 is consumed as follows:
   (1) By plants in photosynthesis.
   (2) It dissolves in water.
       H2O + CO2  H2CO3 (carbonic acid)
       This carbonic acid forms carbonates.
   (3) CO2 directly reacts with CaO present in soil producing calcium carbonate.
       CaO + CO2  CaCO3 (lime)

                                     (Carbon cycle)

(3) NITROGEN CYCLE: Nitrogen is a macronutrient essential for the growth of
living organisms, which cannot be used directly. It is present in air in gaseous
form. This N2 undergoes fixation and converts to the organic compounds required
by the plants and animals. The cycle of nitrogen in nature passes through various
stages which are as follows in sequence: (1) Nitrogen fixation, (2) Assimilation, (3)
Ammonification, (4) Nitrification and (5) De-nitrification.


a)    Nitrogen Fixation: The      first step is the most important form and takes
place by various methods: -       (i) Electrification: In nature during electrical
discharge of clouds, the oxygen   molecules split into its 2 atoms. It combines with
the gaseous nitrogen producing    various oxides as shown below with the help of
chemical equation:

                              O2  2[O] (electrification)
                                   N2 + 2 [O]  2 NO
                                 2 NO + 2 [O]  2 NO2
                                  2 NO2 + [O]  N2O5
The oxidation of nitrogen dissolves in water during rainfall producing nitric acid.
                              N2 O5 + H2O  2 HNO3
This acid when falls on the earth’s surface combines with the bases of the soil
producing nitrates:
                   2 HNO3 + 2 CaCO3  Ca(NO3)2 + CO2 + H2O

  (ii)Biological Fixation: The nitrogen in the oceans, lakes and in the soil takes
  place by blue-green algae. At the same time, symbiotic bacteria present in the
  roots modulus of leguminous plants also fix the nitrogen. Nitrogen is also fixed
  in form of ammonia (NH3).
                               N2 + 3H2  2 NH3

b) Assimilation: Accumulation or collection of compounds of nitrogen n the soil.
c) Ammonification: Conversion of nitrogen or the oxides of nitrogen into
   ammonia, which mainly occurs by ammonifying bacteria.
d) Nitrification: Formation of nitrides and nitrates, one of the causes is bacteria.
   For e.g. Nitrosomonas.
e) De-nitrification: It occurs due to bacteria. For e.g. Nitrobacter.

 Due to the expansion of agriculture and to fulfill the needs of growing population,
there is a continuous demand of ammonia as a nutrient, so it is added as a
chemical fertilizer e.g. ammonia nitrate [NH4NO3].

                                      (N2 cycle)
(4) OXYGEN CYCLE: Oxygen, a vital gas, passes through different stages in the
natural cycle directly through the living-beings in a very simple way. But without


oxygen none of the process is possible. The flow of oxygen within the biosphere
and outside it occurs in two major steps:
i. Production of oxygen:
      a) Photosynthesis
      b) Photolysis of water
      c) Splitting of ozone into oxygen and nascent oxygen.
   O3  O2 + [O]

ii. Consumption of Oxygen:
      a) Respiration by plants and animals.
      b) Decomposition of sediments and dead organic matter.
      c) Combustion of fuel.
      d) Natural forest fire.

                               (Oxygen cycle)
The oxygen from atmosphere and the organic compound from the soil are
consumed by the biosphere. The oxygen burns the food and produces the ultimate
products, CO2 and H2O. These compounds are again utilized by plants for
production of food through photosynthesis liberating oxygen again in the

(5) SULPHUR CYCLE: Sulphur in atmosphere is present as sulphur dioxide
(SO2). This SO2 is converted to sulphates and sulphides, the compounds which
can be easily absorbed by the plants. These plants in turn are consumed by
animals. After death and decay they convert back to sulphur dioxide (SO 2). For the
invitation of this cycle, SO2 is required. In nature SO2 is produced by the following
    a) Oxidation of sulphur, which is found under the earth crust associated with
    b) Oxidation of H2S (H2S is produced by decomposition of sewage).
    c) Weathering of rocks.
    d) Grassland and forest-fires.
    e) Decomposition of organic matter.

  Conversion into sulphates and sulphides:
   SO2 dissolves in rain water producing sulphurous (H2SO3) and sulphuric acid
   (H2SO4). This are easily converted into salts when they come in contact with
   the soil.

The flow of energy in an eco-system takes place essentially which keeps it going.
The unique feature of this is that it is unidirectional i.e. it can’t be reused. The flow
of energy follows 2 laws of thermodynamics: -
    [1] Energy is neither created nor destroyed. It is only transformed from one
        form to the other. For e.g. energy from the sun is trapped by the plants
        through photosynthesis and converted into biochemical energy. It is
        consumed by plant itself for its growth and movement i.e. the energy
        changes into the chemical and mechanical energy. When these plants are
        eaten by consumers, the chemical energy gets converted into mechanical
        energy. Thus we see changes in the types of energy.
    [2] The energy dissipates i.e. it moves from higher concentration to the lower
        concentration. The energy in the ecosystem flows from one level to the
        other. During this flow almost 90% of the loss takes place i.e. only 10%
        energy is transformed.

The flow of energy in the ecosystem takes place in the food chain.

The process of eating and being eaten is known as FOOD CHAIN. Every
organism whether dead or living, serves as a potential food for the other organism.
For e.g.
    Leaves  caterpillar  sparrow  cat  hawk  decomposers.
Every consumer in the food chain is assigned a feeding or trophic level depending
upon its nutritional status. As in above example the caterpillar which lives on
leaves occupies the first trophic level, sparrow the second, cat the third and hawk
the fourth. The energy as we discussed earlier flows from caterpillar to the hawk
through different levels. In nature 2 types of food chain exists.

(1)      Grazing food chains:
      Grass  grasshopper  frog  snake  hawk/eagle  decomposers.


Such type of food chain derives energy from the green autotrophic plants passing
through different levels; finally the dead organic matters or animals are
decomposed by bacteria and fungi and converted to the nutrients which are used
again by the plants. This is an example of ‘grassland food chain’.

(2)     Detritus food chain:
In such type of food chain the animals depend upon the saprophytes or
detritivores (depend on dead organic matter) i.e. the dead organic matter.

Leaf litter  algae  crabs (molluses/shrimps)  small carnivorous fishes 
large carnivorous fishes  decomposers.

The dead leaves of the plants when fall in the water forms litter (waste), these are
colonized by algae. These in turn are eaten by higher detritivores crabs, molluses
and shrimps. These are consumed by small carnivorous fishes and further by
large carnivores fishes. After their death bacteria and fungi again act and convert
into simpler compounds e.g. mangrove ecosystem and estuarine ecosystem.
Both types of food chains exist in nature. But usually the grazing food chain is

The food chains instead of operating in linear sequences are interconnected at
various trophic levels and form a complex network. Thus, food web is defined as a
network of large number of eating and non-eating organisms at various
trophic levels. We can understand this with the help of a terrestrial food web.


 Food web in nature gives greater stability to any ecosystem, because if any
 species of the organism becomes extinct, the successive trophic level
 do s ’t suff .

 Simplest example of food web showing the inter-linking of 5 food chains is shown

  a. Abiotic Components: It includes the organic and inorganic nutrients in the soil
     and atmosphere. Besides this the large amount of dead organic debris is found.
     The conditions of sunlight changes drastically due to stratification (layering) of
     the trees. Depending upon the conditions of the atmosphere in a region mainly
     3 kinds of forest are found: (1) Tropical, (2) Sub-Tropical and (3) Temperate.
  b. Biotic Components:
  i. Producers: Big tress, plants, few shrubs and grasses.
 ii. Consumers: (a) Primary consumers: These are insects, beetles, ants and
     spider which feed on leaves of small grass. Some herbivores like moose feed
     on the broad leaves of the plants and trees. Large herbivores like elephant and
     deer feed on the shoot and fruits of trees. (b) Secondary consumers: They are
     mainly the insectivorous birds. (c) Tertiary consumers: They are top carnivores
     like lion and tiger.
iii. Decomposers: Large variety of bacteria and fungi exists under the soil
     responsible for decomposition of dead organic matter. The rate of
     decomposition is much more rapid in the tropical and sub-tropical forest.

  a. Abiotic Components: These are minerals like carbon, hydrogen, oxygen,
     nitrogen, phosphorous obtained from the soil and air in the form of water,
     carbon dioxide, sulphates, phosphates and nitrates. The grassland exists in the
     interior of continents. The rainfall is found to be 25-75%.
  b. Biotic components:
  i. Producers: Mainly grass with small shrubs.
 ii. Consumers: (a) Primary consumers: Mainly the grazing animals like cow,
     buffalo, goat, deer and some insects like ants and termites. (b) Secondary
     consumers: They feed on herbivorous animals. They are small carnivores like
     fox, lizard, snake and jackal. (c) Tertiary consumers: These are mainly large
     carnivores birds like hawk and eagle.
iii. Decomposers: These are bacteria and fungi. Different bacteria and fungi
     decompose and return the elements back to the soil.

  a. Abiotic Components: The deserts exist in the driest region of the environment.
     The extremely high temperatures are in the hot deserts. For example Sahara,
     Arabia-Gobi desert complex. The extremely low temperature is in the cold
     desert, for example Ladakh region of Himalayan range. The rainfall is negligible
     and insignificant i.e. less than 10 mm. The humidity in the air is also very low
     due to high rate of evaporation.
  b. Biotic Components:
  i. Producers: These are small bushes, shrubs, very few grass, trees, Succulent
     (mean. They store water) plants like cactus, some xerophytic (xero=dry,
     phytic=plants) mosses and lichens.
 ii. Consumers: Nocturnal birds and rodents (which live in soil) like camel, feed on
     tender leaves of the trees.
iii. Decomposers: The decomposers are very few, they are mainly thermophilic
     (temperature loving) bacteria, which decompose the dead organic matter which
     are very less in quantity.

 a. POND ECOSYSTEM: This is an example of fresh water ecosystem. It is a self-
    sufficient and self-regulating system which has its usual components.
 i. Abiotic components:
    Heat, light, pH, dissolved oxygen, oxygen, carbon dioxide, nitrates, sulphates
    and phosphates are the components which vary depending upon location of the
    pond. These all are responsible for providing the nutrients to the producers.
ii. Biotic components:
    (1) Producers:
    These are photo-autotrophic green plants. They can be classified into two: (a)
    Macrophytes: These are large rooted plants, some time present on margin of
    the pond. They are known as hydrophytes. Few free floating plants are also
    present, for example water hyacinth and lotus. (b) Phytoplanktons: These are
    microscopic, photosynthetic plants like algae.

    (2) Consumers:
    i. Primary consumers: The primary consumers are of two kinds:
    a. Benthos: These are bottom dwelling insect larvae and some reptiles.
    b. Zooplanktons: These are crabs, molluses and shrimps.
   ii. Secondary consumers: They are rotifers and small carnivorous fishes.
  iii. Tertiary consumers: They are large carnivorous fishes.

   (3) Decomposers:
   They are mainly bacteria and fungi.

 b. MARINE ECOSYSTEM: Almost 70 % of earth’s surface is covered by such type
    f water i.e. sea and oceans.
 i. Abiotic Components:
    Concentration of soil, minerals like calcium, phosphates, sulphates, and pH do
    not vary much.

ii. Biotic Components:
 (1) Producers: Algae, diatoms. Varieties of algae are red and green.
 (2) Consumers: Consumers in series are zooplanktons, rotifers, crush-stations,
     protozoan, small carnivorous fishes, large carnivorous fishes. Examples of
     small carnivorous fishes are shad and herring. Examples of large carnivorous
     fishes are haddock and halibut.
 (3) Decomposers: Mainly bacteria decompose dead organic matter.

   Estuarine: It is a semi-enclosed coastal water-body, which has a free
   connection with the sea water.
   The estuarine is affected by tidal waves.
   (1) Producers: Phytoplankton.
   (2) Consumers: zooplanktons, crustaceans, small fishes and large fishes.
   (3) Decomposers: Bacteria.

 Ecological Pyramid was studied by a British ecologist Charles Elton
   (1927) and therefore is also called Eltonion pyramids.
 There is a relation of number and mass of the organisms at each trophic level
   with the available energy.
 Ecological pyramids are defined as graphical representation of an ecological
   structure and function which generally shows a broad base and becomes
   narrow at apex.
 An ecological pyramid is a graphical representation of an ecological
   parameter like number of individual or amount of biomass or amount of
   energy present in various trophic levels of food chain with producer
   forming the base and top carnivores the tip.
 For example for general food chain like “Producers  consumers (herbivores)
    primary carnivores  top carnivores (decomposers)”, there are three types
   of pyramid:
(1) Number Pyramid: This pyramid relates the number of organisms at each
    trophic level.
    (a) Grassland Ecosystem: (i) Producers: grass, shrubs, and trees.
                               (ii) Primary consumer: rabbit, mouse and
                               (iii) Secondary consumer: lizard and consumer.
                               (iv) Tertiary consumer: hawk and eagle.

                                        1 consumer



    Such type of pyramid is known as slopping/upright/straight pyramid.

    (b) Pond Ecosystem:         (i) Producers: Phytoplankton.
                                (ii) Primary consumer: crabs, mollusks, shrimp.
                                (iii) Secondary consumer: small carnivorous
                                (iv) Tertiary consumer: large carnivorous fishes.

    (c) Forest Ecosystem:       (i) Producers: Trees.
                                (ii)Primary consumer: birds.
                                    Secondary consumer: reptiles, snakes.
                                (iv)Tertiary consumer: small carnivorous animals,
                                    fox and jackal.
                                (v) Quaternary consumer: lion and tiger.

                                              2 consumer

                                              1 consumer


This pyramid has narrow base, broad in middle and narrow at apex (spindle-

    (d) Parasite Ecosystem:     (i)     Producers: Tree.
                                (ii)    Primary consumer: birds.
                                (iii)   Secondary consumer: lice and bugs.
                                (iv)    Tertiary consumer: hyperparasites.
                                (v)     Quaternary consumer: flea and microbes.

                                         4 consumer

                                         3 consumer

                                          2 consumer



It is an Inverted pyramid; it has narrow base and broad apex.


   The number pyramid does not give the actual picture because in a community
   large number of food chain exists, which vary.

(2) Biomass Pyramid:
     It deals with the study of biomass (dry weight) of organisms with each trophic
     This type of study shows that the pyramid for grassland and forest is upright or
     It has broad and narrow apex.

                               Hawk/eagle          Hawk/eagle

                                 Reptiles         Snake/ lizard

                                  Birds              rabbit/ mouse

                                  Trees                  Grass

    But for biomass pyramid for pond eco-system is inverted.
                                  Large carnivorous


(3) Energy Pyramid:
 As we know from the study of flow of energy that at each successive trophic
    levels, almost 90% of energy is lost as heat and respiration, only 10% is
    transferred i.e. if the energy of trophic levels is related, the pyramid formed is
    always of slopping kind (upright) for any ecosystem.



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Description: ENVIRONMENTAL STUDIES (EVS) Gujarat Technological University GTU 1st year subject notes